CN114222829B - System and method for aqueous recovery of lead from lead acid batteries with reduced electrolyte requirements - Google Patents

System and method for aqueous recovery of lead from lead acid batteries with reduced electrolyte requirements Download PDF

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CN114222829B
CN114222829B CN202080057142.5A CN202080057142A CN114222829B CN 114222829 B CN114222829 B CN 114222829B CN 202080057142 A CN202080057142 A CN 202080057142A CN 114222829 B CN114222829 B CN 114222829B
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lead
plaster
desulphurised
electrolyte
heating
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CN114222829A (en
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萨玛列什·莫汉塔
J·赫福德
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Aqua Metals Inc
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B13/00—Obtaining lead
    • C22B13/04—Obtaining lead by wet processes
    • C22B13/045—Recovery from waste materials
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
    • C25C1/18—Electrolytic production, recovery or refining of metals by electrolysis of solutions of lead
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/54—Reclaiming serviceable parts of waste accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/06—Lead-acid accumulators
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G21/00—Compounds of lead
    • C01G21/02—Oxides
    • C01G21/06—Lead monoxide [PbO]
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/005—Preliminary treatment of scrap
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/02—Roasting processes
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/11—Removing sulfur, phosphorus or arsenic other than by roasting
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
    • C25C7/007—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells of cells comprising at least a movable electrode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/56—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of lead
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/10—Process efficiency
    • Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/84—Recycling of batteries or fuel cells

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  • Metallurgy (AREA)
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  • Inorganic Chemistry (AREA)
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  • Processing Of Solid Wastes (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Electrolytic Production Of Metals (AREA)

Abstract

Lead is recovered from the lead paste of a lead acid battery in a continuous electrochemical lead recovery process. In a particularly preferred aspect, the lead plaster is processed to remove residual sulphate and the lead plaster so treated is subjected to a heat treatment step to remove residual moisture and reduce lead dioxide to lead monoxide. Advantageously, such pretreatment will avoid lead dioxide accumulation and electrolyte dilution.

Description

System and method for aqueous recovery of lead from lead acid batteries with reduced electrolyte requirements
Cross Reference to Related Applications
The present application claims priority from U.S. provisional application No.62/860928 filed on day 13, 6, 2019, which is incorporated herein by reference in its entirety.
Technical Field
The field of the application is an improved process for recovering lead from desulphurised lead paste using an electrolytic process, and in particular the application relates to the protection of electrolyte and water balance in such recovery processes.
Background
The description of the background art includes information that may be used to understand the present application. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed application, or that any particular or implicitly referenced publication is prior art.
All publications identified herein are incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference does not conform to or is contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
Various efforts have been made to break out of the smelting operations in recycled Lead Acid Batteries (LAB) and to use more environmentally friendly solutions. For example, U.S. patent No.4927510 teaches recovery of substantially all of the lead in pure metallic form from the battery sludge after the desulfurization process. In another example, canadian patent No.1310837 also teaches recovery of lead in metallic form from desulfurization pastes. Leaching the paste with an acid suitable for electrowinning and using hydrogen peroxide to dissolve the insoluble PbO 2 And (5) reduction. Unfortunately, the '510 and' 837 patents require the use of a fluorine-containing electrolyte (e.g., fluoroboric acid or fluorosilicic acid), which is also problematic.
To overcome some of the difficulties associated with the fluorine-containing electrolytes, as described in U.S. patent No.5262020 and U.S. patent No.55520794, the desulphurised lead active material is dissolved in methane sulphonic acid. On the other hand, lead recovery in methanesulfonic acid can also be performed without desulfurization as described in International patent publication No. WO 2015/077227. Here, it has been found that inclusion of a chelating agent with a solvent such as MSA (e.g. EDTA) increases the solubility of lead oxide and lead sulfate salts at acidic pH, allowing recovery of lead from such solvents by electrodeposition. As will be appreciated, lead dioxide remains insoluble in such solvents. In addition, when the lead material has been previously desulphurised (e.g. using sodium hydroxide to form soluble sodium sulphate), then the pretreated lead plaster still contains significant amounts of residual sulphate and aqueous desulphurisation medium, which in turn causes contamination and dilution of the downstream electrolyte used in lead recovery.
Hydrogen peroxide may be used to reduce lead dioxide as described in U.S. patent No.8409421, which teaches an electrolytic process for recovering lead from desulphurised lead paste. Here, the lead paste is leached with a solution containing ammonium chloride to form a two-phase reaction product. Leaching the solid phase of the reaction product with hydrogen peroxide to reduce insoluble PbO 2 And a second two-phase reaction product is formed.The liquid phases of the two reaction products are subjected to electrolysis to form metallic lead. However, although the amount of lead dioxide is significantly reduced in such liquid processes, the water demand is not insignificant and the presence of water dilutes the electrolyte, thereby increasing the requirements and cost of the electrolyte. Similar problems are also encountered in continuous lead recovery processes and are often amplified as described in applications US 2017/0352927, US 2018/0127152 and US 2018/0355494.
Thus, while various methods of recovering lead using electrolytes are known in the art, all or almost all methods suffer from one or more drawbacks. Most notably, while these methods avoid environmental problems associated with smelting operations, new difficulties arise in electrolyte management and lead dioxide reduction. Thus, there remains a need for improved non-smelting recovery processes for lead acid batteries, particularly in a manner that avoids lead dioxide accumulation, electrolyte contamination, and/or electrolyte dilution.
Disclosure of Invention
The present subject matter relates to various systems and methods for avoiding lead dioxide accumulation, electrolyte dilution and contamination, particularly in a smelting-free electrochemical lead recovery process.
In one aspect of the inventive subject matter, the inventors contemplate a method of reducing electrolyte loss in an electrochemical lead recovery operation for recovering metallic lead from a desulfurized lead-acid battery lead plaster. The method has the step of providing a desulphurised lead plaster, wherein the desulphurised lead plaster comprises lead dioxide (lead dioxide), lead monoxide (lead oxide), lead hydroxide and/or lead carbonate, and further comprises residual sulphate. The method includes a washing step in which the desulphurized lead paste is washed with water, thereby forming a washed desulphurized lead paste with residual water. The method includes heating the washed desulphurised lead plaster to reduce residual water to 10wt% or less and reducing at least 50% of the lead dioxide to lead monoxide to form a dried, decomposed desulphurised lead plaster. In a further step, the dried decomposed and desulphurised lead plaster is combined with a recycled (electrolyte) to form a lead ion-enriched electrolyte, and in a further step the lead ion-enriched electrolyte is subjected to an electrochemical lead recovery operation to recover metallic lead at the cathode and produce a recycled electrolyte.
For example, the desulphurized lead paste may be desulphurized using an aqueous base and/or may comprise residual lead sulphate in an amount of 0.1wt% to 10 wt%. It is also contemplated that the desulphurized lead plaster is subjected to a pressure filtration step prior to the heating step, if desired.
Further embodiments include removing residual water from the washed desulphurised lead plaster. Preferably, removing water from the washed desulphurised lead plaster comprises pressure filtration and/or using waste heat from the step of heating the washed desulphurised lead plaster.
In some embodiments, the step of washing the desulphurised lead plaster reduces the amount of residual sulphate in the washed desulphurised lead plaster by at least 50%, at least 70% or at least 90% compared to the desulphurised lead plaster prior to washing.
In some embodiments, the step of heating the desulphurised lead plaster reduces the residual water to equal to or less than 10wt%, equal to or less than 5wt%, or equal to or less than 2wt%, and the step of heating the desulphurised lead plaster may reduce at least 25%, at least 50%, at least 70%, or at least 90% of the lead dioxide to lead monoxide. In a further embodiment, the heating step is performed in a kiln such that the temperature of the material at the end of heating is 400 ℃ to 700 ℃ or 500 ℃ to 560 ℃. For example, heating may be performed for a period of time ranging from 5 minutes to 15 minutes (e.g., measured between the end of the product entering the feed end or rotary kiln and exiting the rotary kiln). It is further contemplated that the recycled electrolyte may comprise alkane sulfonic acids, such as methane sulfonic acid.
Optionally, the method of reducing electrolyte loss includes the step of removing solids from the lead ion-enriched electrolyte and/or the recycled electrolyte. For example, the solid comprises at least one of lead dioxide, lead sulfate, or grid lead.
Typically, but not necessarily, electrochemical lead recovery operations use a moving cathode. In this case, the electrochemical lead recovery operation may include the step of reducing lead ions on one portion of the cathode while removing metallic lead from another portion of the cathode. Can be removed from the lead ion-enriched electrolyte and/or the recycled electrolyte as needed or desiredRemoving residual lead sulfate. Preferably, the metallic lead has a purity of at least 95wt%, or at least 97wt%, or at least 99 wt%. In addition, the density of the recovered metallic lead is less than 5g/cm 3 Or less than 2g/cm 3 。
In another aspect of the inventive subject matter, the inventors contemplate a method of reducing lead dioxide accumulation in an electrochemical lead recovery operation that recovers metallic lead from a lead paste of a lead acid battery and uses and recycles an electrolyte in which lead dioxide is insoluble. Preferably, such a method will include the steps of providing a lead plaster, wherein the lead plaster comprises lead dioxide and no more than 2.0wt% residual sulphate, and the further step of heating the lead plaster to reduce at least 25% of the lead dioxide to lead monoxide, thereby forming a decomposed lead plaster, and the further step of combining the decomposed lead plaster with a recycled electrolyte to form a lead ion-enriched electrolyte. In a further step, the electrolyte enriched in lead ions is subjected to an electrochemical lead recovery operation, whereby metallic lead is recovered at the cathode and a recycled electrolyte is produced.
In some embodiments, the lead paste is a desulphurized lead paste. Contemplated lead pastes may also contain residual water in an amount of at least 10 wt%. As will be appreciated, the lead plaster may be subjected to a pressure filtration step prior to the heating step.
In a further embodiment, the step of heating the lead plaster reduces at least 60% or at least 70% or at least 90% of the lead dioxide to lead monoxide. In addition, the step of heating the lead paste may reduce the residual water to 10wt% or less, 5wt% or less, or 2wt% or less. The heating may be carried out in a kiln such that the temperature of the material at the end of the heating is 400 to 700 ℃ or 500 to 560 ℃. Preferably, but not necessarily, the recycling electrolyte comprises alkane sulfonic acid (e.g., methane sulfonic acid).
In other embodiments, the method of reducing lead dioxide accumulation in electrochemical lead recovery may include the step of removing solids from the lead ion-rich electrolyte and/or the recycled electrolyte. For example, the solid comprises at least one of lead dioxide, lead sulfate, or grid lead.
In yet another embodiment, the electrochemical lead recovery operation uses a moving cathode. In this case, the electrochemical lead recovery operation may include the step of reducing lead ions on one portion of the cathode while removing metallic lead from another portion of the cathode. Contemplated methods further include the step of removing residual lead sulfate from the lead ion-enriched electrolyte and/or the recycled electrolyte, if desired. Most typically, the metallic lead has a purity of at least 95wt%, or at least 97wt%, or at least 99 wt%. The recovered metallic lead has a content of less than 5g/cm 3 Density of (2) or less than 2g/cm 3 Is a density of (3). The method presented herein may also include the further step of casting metallic lead, if desired. Furthermore, it is contemplated that water may be collected (and reused) from the heating step or from the step of pressure filtering the lead plaster prior to the heating step.
In other embodiments, in a continuous electrochemical lead recovery operation for recovering metallic lead from a desulphurised lead acid battery lead plaster, a method of maintaining an effective concentration of electrolyte and reducing accumulation of lead dioxide in electrolyte includes providing a desulphurised lead plaster, wherein the desulphurised lead plaster comprises lead dioxide, lead hydroxide and/or lead carbonate, and further comprises residual sulphate. The method further includes washing the desulfurized lead paste to form a washed desulfurized lead paste comprising from about 10wt% to about 30wt% residual water present in the desulfurized lead paste. The washed desulphurised lead plaster is then heated to reduce the residual water to 10wt% or less and to reduce at least 50% of the lead dioxide to lead monoxide, thereby forming a dry, decomposed desulphurised lead plaster. The dried decomposed and desulphurised lead paste is then combined with an electrolyte to form a lead ion-enriched electrolyte. The lead ion-enriched electrolyte is subjected to an electrochemical lead recovery operation on a cathode on which metallic lead is formed and recovered, and a recycled electrolyte solution is formed.
In other embodiments, in a continuous electrochemical lead recovery operation for recovering metallic lead from a desulphurised lead plaster, the method of maintaining an effective concentration of electrolyte and reducing lead dioxide accumulation in the electrolyte further comprises heating the washed desulphurised lead plaster in a kiln, wherein the washed desulphurised lead plaster has any shape and does not exceed 1 inch in any dimension.
Various objects, features, aspects and advantages of the present subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawings in which like numerals represent like parts.
Drawings
Fig. 1 is an exemplary illustration of a lead recovery process according to the inventive subject matter.
Fig. 2 is an exemplary graph depicting moisture/weight loss as a function of various temperatures.
Fig. 3 is an exemplary photograph depicting lead in various oxidation states over time at a particular temperature.
Fig. 4 is an exemplary photograph depicting lead in various oxidation states as a function of various temperatures.
Fig. 5 is an exemplary graph depicting the residual amount in the recycled electrolyte after dissolving a heat treated lead plaster sample.
Fig. 6 is an exemplary graph depicting lead ion concentration in a recirculating electrolyte after dissolving a heat treated lead paste sample.
Detailed Description
In the most common process for disassembling Lead Acid Batteries (LAB), lead plaster, plastic and grid lead are produced. The hydraulic separation process of these components then allows the separation of most of the plastic and grid lead, thereby separating the lead plaster. Conventional treatment of lead paste for recovery of metallic lead generally involves desulfurization of the lead paste followed by neutralization with an acid of an acidic solvent. However, in practice, desulphurised lead pastes still include significant amounts of residual sulphate from dissolved sodium sulphate as well as other residual solids (e.g. lead hydroxide, lead monoxide, lead dioxide, grid lead and plastics). Whereas the acid neutralization of the desulphurized paste will readily dissolve lead hydroxide (Pb (OH) 2 ) And lead monoxide (PbO); residual lead dioxide (PbO) 2 ) Residual grid lead and residual plastic remain insoluble; the residual sulfate (e.g., sodium sulfate) will react with methanesulfonic acid (MSA) in the electrolyte to form Na-MSA and lead sulfate, thereby forming a precipitate and reducing the MSA available in the electrolyte solvent.
In addition, considering that the electrolyte is recycled in a continuous process in a preferred lead recovery operation, lead dioxide in the desulphurized lead paste accumulates in the electrolyte, thereby further limiting the effectiveness of recycling the electrolyte solution.
Although washing the desulphurised lead plaster (e.g. with water) may reduce the amount of residual sulphate, the washing water now present in the lead plaster will dilute the electrolyte solution, thereby reducing the effectiveness of recycling the electrolyte solution. More specifically, residual moisture (typically about 10wt% to 30 wt%) from the additional washing step significantly dilutes the electrolyte, thus requiring additional alkane sulfonic acid (e.g., MSA) or removing water from the diluted electrolyte, thereby impeding the usefulness of recycling the electrolyte solution.
With respect to other conventional strategies for treating insoluble residual solids in desulfurized or non-desulfurized lead pastes, heat treatment (e.g., heating) can be used to insolubilize the PbO with acid 2 Is converted into acid-soluble PbO. See, e.g., callder and Simon,1974, j. Electrochem. Soc.,121:1546-1551. However, the residual sulfate salts in the lead plaster are disadvantageous for heat treatment because they generate harmful gases and insoluble lead sulfate, thereby resulting in sulfate-containing lead plaster unsuitable for heat treatment. In addition, the difficulty of heat treatment is further exacerbated by the presence of plastic components remaining in most desulfurized or non-desulfurized diachylons.
Advantageously, contemplated subjects include a process of washing (e.g., washing with water) a desulfurized lead plaster with residual solids, thereby producing a washed lead plaster with reduced residual solids, particularly a washed lead plaster with reduced or removed residual sulfate. For example, the desulphurised lead paste may be subjected to a washing step to remove the alkaline solution with dissolved sodium sulphate (for example in the case of desulphurisation using sodium hydroxide or carbonate). Typically, the washing step reduces the amount of residual sulfate in the desulphurised lead plaster by at least 50wt%, or at least 70wt%, or at least 90wt%, compared to lead plaster that has not been washed (e.g. with water). More specifically, the washing step reduces the amount of residual sulfate in the desulfurized lead plaster by at least 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 71wt%, 72wt%, 73wt%, 74wt%, 75wt%, 76wt%, 77wt%, 78wt%, 79wt%, 80wt%, 81wt%, 82wt%, 83wt%, 84wt%, 85wt%, 86wt%, 87wt%, 88wt%, 89wt% or 90wt%. Alternatively or additionally, the washing step may reduce the amount of residual sulfate in the desulfurized lead paste to an amount of about 0.1wt% to about 10wt%, 0.1wt% to 2wt%, 0.1wt% to 1wt%, 0.1wt% to 0.7wt%, 0.5wt% to 0.7wt%, or 0.1wt% to 0.5 wt%. More specifically, the washed desulphurized lead paste contains residual sulphate in an amount of about not more than 5wt%, not more than 4wt%, not more than 3wt%, not more than 2wt%, not more than 1.9wt%, not more than 1.8wt%, not more than 1.7wt%, not more than 1.6wt%, not more than 1.5wt%, not more than 1.4wt%, not more than 1.3wt%, not more than 1.2wt%, not more than 1.1wt%, not more than 1wt%, not more than 0.9wt%, not more than 0.8wt%, not more than 0.7wt%, not more than 0.6wt%, not more than 0.5wt%, not more than 0.4wt%, not more than 0.3wt%, not more than 0.2wt%, or not more than 0.1 wt%. Typically, the washed desulphurised lead plaster contains residual sulphate in an amount of about 0.5wt% to 2.5wt% and most typically not exceeding 2.0 wt%.
Notably, the washed lead paste includes an electrolyte diluted wash solution; however, since the residual sulphate has been removed/reduced, the washed lead plaster may now be heated by heat treatment, thereby removing additional washing solution (e.g. water) and at least 25% and at most at least 90% of the lead dioxide (PbO) in the washed lead plaster 2 ) Is converted into lead monoxide (PbO). Thus, contemplated methods effectively allow for reduced electrolyte loss/dilution and reduced accumulation of acid insoluble lead dioxide (and lead sulfate) in lead recovery operations that recover metallic lead from washed desulphurised lead paste. In addition, the washed desulphurised lead plaster may be subjected to a step of reducing the moisture content (e.g. water content) prior to heat treatment, such as pressure filtration and/or heating using recycle process heat from the heat treatment step.
From a different perspective, the inventors have now found that an electrochemical lead recovery process, particularly a continuous electrochemical lead recovery process in which the electrolyte is recycled and reused, can be significantly improved by pre-treating the desulphurised lead paste to avoid the difficulties associated with dilution of the electrolyte and accumulation of lead dioxide in the recycled electrolyte. Advantageously, the pretreatment of the lead plaster with a water content of at least 10wt% (e.g., 10wt% to 30 wt%) and a sulfate content of not more than 2.0wt% by heat treatment is environmentally friendly, can be performed in a continuous manner, and will produce a fully dried and decomposed lead plaster suitable for dissolution in a suitable electrolyte (e.g., an acidic electrolyte such as sulfuric acid, methanesulfonic acid, fluoroboric acid, etc., or an alkaline electrolyte such as a concentrated NaOH solution). Preferably, the water content of the dried and decomposed lead paste after the heat treatment is equal to or less than 10wt%. More preferably, the moisture content of the dried and decomposed lead paste after heat treatment is not more than 9.5wt%, 9wt%, 8.5wt%, 8wt%, 7.5wt%, 7wt%, 6.5wt%, 6wt%, 5.5wt%, 5wt%, 4.5wt%, 4wt%, 3.5wt%, 3wt%, 2.5wt%, 2wt%, 1.5wt% or 1wt%. Most preferably, the water content of the dried and decomposed lead plaster after heat treatment is not more than 5wt% or not more than 2wt%.
In addition, the dried and decomposed lead plaster after the heat treatment is at least 25% less lead dioxide than the lead plaster before the heat treatment. That is, the amount of lead dioxide of the heat treated (e.g., heated) lead paste is reduced by at least 25%, and typically, the amount of lead dioxide of the heat treated lead paste is reduced by at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, or at least 97% as compared to the lead dioxide content of the lead paste prior to the heat treatment. In addition to the heat treatment, as disclosed herein, the pretreatment may also include washing the lead paste, wherein the lead paste is a desulfurized lead paste or a non-desulfurized lead paste, and washing to remove residual solids (e.g., sulfate) prior to the heat treatment.
In particularly preferred methods, the pretreatment is a thermal pretreatment step wherein the water content of the lead plaster prior to the thermal treatment is at least 10wt% (e.g., 10wt% to 30wt%, 10wt% to 25wt%, 10wt% to 20wt%, 10wt% to 15wt%, 12wt% to 14wt%, 12wt% to 13wt%, 10wt% to 14wt%, or 10wt% to 13 wt%). As will be readily appreciated, the water content may be adjusted by various means (e.g., filtration, pressure filtration, centrifugation, solvent exchange, etc.) Amount of the components. In preferred embodiments, the washed lead paste prior to heat treatment has a water content of no more than 15wt%, no more than 14wt% or no more than 13 wt%. The washed lead paste is then thermally dehydrated and decomposed such that the treated lead paste has a significantly reduced water content (e.g., 10wt% or less, 9wt% or less, 8wt% or less, 7wt% or less, 6wt% or less, 5wt% or less, less than 5wt%, or less than 4wt%, or less than 3wt% or less than 2 wt%) and a significantly reduced lead dioxide content (e.g., less than 10wt%, or less than 7wt%, or less than 5wt%, or less than 3 wt%). Typically, the thermal pretreatment reduces the amount of lead dioxide in the treated lead paste by at least 60%, at least 70%, at least 80%, at least 90%, at least 95% or at least 97% of the total lead dioxide as compared to the lead dioxide in the lead paste prior to the thermal treatment, making it an oxide other than lead dioxide (i.e., alpha-PbO x 、β-PbO x 、(x<2)Pb 3 O 4 PbO (tetragonal), pbO (orthorhombic)).
Furthermore, the thermal pretreatment will in some cases reduce the amount of plastic components by thermal decomposition. Most advantageously, the envisaged thermal pretreatment eliminates the need to reduce lead dioxide insoluble in most electrolytes and avoids electrolyte dilution. From a different perspective, the relatively small amount of residual undissolved solids in the electrolyte combined with the pretreated lead paste is mainly lead sulfate, which can be readily subjected to conventional desulfurization steps, which can be part of the lead recovery operation or can be a separate process.
In one exemplary embodiment of the inventive subject matter, as shown in fig. 1, a battery recycling apparatus (plant) generally includes a disassembly station in which the battery is disassembled and crushed to a suitable size for further processing. The disassembly station will also perform an initial separation of the various components to remove the liquid phase (mainly sulfuric acid and dissolved substances), grid lead and plastic particles using conventional separation methods. The remaining lead paste (mainly comprising lead monoxide, lead dioxide and lead sulphate) may then be subjected to a desulphurisation step. In an exemplary aspect, desulfurization is performed using a base such that lead sulfate is converted to insoluble lead hydroxide (or carbonate), thereby forming soluble sodium sulfate. Most typically, lead dioxide is not reactive under these conditions and remains an insoluble component. While this desulfurization step will remove a substantial proportion of the lead sulfate, it will be appreciated that the residual lead sulfate will remain in the paste as well as residual dissolved sodium sulfate (this is generally not problematic in processes other than continuous processes using recycled electrolyte). The continuous process of recovering lead from a lead acid battery, in which the electrolyte is recycled and the process is repeated continuously, may also be referred to as a "closed loop process".
After removing a major portion of the soluble sodium sulfate from the insoluble paste in the desulfurization process, the paste/precipitate is then subjected to a washing step, which typically involves reslurrying the desulfurization paste with an aqueous solvent. As disclosed throughout, the washing step will advantageously reduce the sulfate concentration (and residual plastic content) in the washed paste. If desired, the wash paste may be subjected to a further moisture removal step, typically in a filter press. Alternatively or additionally, waste heat from the heat treatment may be used to evaporate at least some of the water present in the washed paste. As should be readily appreciated, all of the removed water may be recycled to the apparatus and used in various process steps (e.g., as make-up water for new electrolytes) to reduce overall water requirements. The soluble sulfate salts in the wash water may be removed in a variety of ways, including precipitation, crystallization, or by ion exchange, as desired or required.
Notably, in some embodiments, the heat treatment is a continuous heat treatment using a rotary kiln that converts at least 25%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least 97% of all the lead dioxide to an oxide other than lead dioxide (i.e., alpha-PbO x 、β-PbO x 、(x<2)Pb 3 O 4 PbO (tetragonal), pbO (orthorhombic)). Preferably, the heat treatment produces mainly Pb 3 O 4 And PbO (tetragonal), and most preferably predominantly PbO (tetragonal). For example, at a preferred heatAfter the treatment process, the residual lead dioxide is present in a concentration of equal to or less than 10wt%, equal to or less than 8wt%, equal to or less than 6wt%, equal to or less than 4wt%, equal to or less than 2wt%, equal to or less than 1wt%, while at least 70wt%, at least 80wt%, at least 85wt%, at least 90wt%, or at least 95wt% of PbO (tetragonal form) is formed from lead dioxide, the remainder preferably Pb 3 O 4 As the primary lead oxide species. From a different perspective, at least 80%, at least 85%, at least 90% of the total lead dioxide will be converted to PbO (tetragonal form) and/or Pb 3 O 4 . Advantageously, all of these non-lead dioxide materials are soluble in alkane sulfonic acids (e.g., methane sulfonic acid) and thus can be electrochemically recovered in a process that does not require a chelating agent to dissolve lead sulfate. Furthermore, particularly in the case of desulfurization and thermal decomposition, it will be appreciated that all of the lead species so produced are suitable for recycling to extinction in the process described herein (i.e., residual amounts of insoluble lead sulfate may be fed to the desulfurization operation, residual amounts of lead dioxide may be fed to the thermal treatment, etc.).
]For this reason, the heat treatment generally requires heating the lead paste for a sufficient time and temperature to decompose the lead dioxide into α -PbOx, β -PbOx, (x)<2)Pb 3 O 4 PbO (tetragonal) and/or PbO (orthorhombic), and evaporating most or all of the residual water. For example, as discussed in more detail below, a suitable temperature is at least about 190 ℃, or at least about 350 ℃, or at least about 400 ℃, or at least about 460 ℃, or at least about 530 ℃, or at least about 550 ℃, or at least about 560 ℃. Thus, suitable heating temperatures will range from 350 ℃ to 550 ℃, or 450 ℃ to 570 ℃, or 480 ℃ to 580 ℃, or 500 ℃ to 575 ℃. The heating material is analyzed in various ways and a suitable heating time can be easily determined. However, since different lead species will have different colors, as shown in more detail below, the heating temperature and duration may be adjusted so that this dry decomposed lead plaster is predominantly yellow, which is indicative of tetragonal forms of lead monoxide.
Notably, the lead paste may be heated using any suitable heating process/technique for a time and at a temperature sufficient to decompose the lead dioxide. In exemplary embodiments, heating of the lead paste is performed using batch heating, a fluidized bed reactor for continuous heating, a conveyor oven, a moving heat source, or a rotary kiln. Although any suitable heating process may be used and readily adapted to heat the lead plaster to remove residual water and convert lead dioxide to lead monoxide, a rotary kiln is preferred because it breaks up aggregates in the lead plaster, thereby releasing moisture and increasing the efficiency of the removal of water from the lead plaster.
Once the heat treatment reaches the desired product composition (e.g., dry decomposed lead plaster), the treated lead plaster is cooled and then dissolved in an appropriate solvent/electrolyte as needed. While many electrolytes are well known in the art, it is generally preferred that the electrolyte be an alkane sulfonic acid (especially methane sulfonic acid) or a strong base (in a concentration sufficient to produce a soluble lead acid salt). After dissolution of the treated lead paste, a lead ion-rich electrolyte is formed, followed by electrochemical reduction, wherein the lead ions are reduced at the cathode to form metallic lead. Most preferably, the cathode is a moving cathode (e.g., a disk-type cathode) on one portion of which lead is reduced and at the same time metallic lead is harvested from another portion of the cathode, typically as a micro-and nanostructured metallic lead product. Most typically, the lead so produced is high purity lead, at least 95%, more typically at least 97%, or at least 98%, or at least 99%. In addition, the density of the recovered high purity lead is less than 5g/cm 2 Less than 4g/cm 2 Less than 3g/cm 2 Or less than 2g/cm 2 . Particularly preferred systems and methods of such lead production are described in US 2017/0352927, US 2018/0127152 and US 2018/0355494, which are incorporated herein by reference.
Thus, it should be appreciated that a continuous electrochemical lead production process may provide pretreated lead plaster, which is also provided in a continuous manner. Once the metallic lead is recovered in the desired amount, the electrolyte has a significantly reduced lead ion concentration (lead ion depleted electrolyte) and can be recycled to the process to dissolve the further pretreated lead plaster. Advantageously, the addition of a pretreated, dried decomposed lead plaster does not significantly increase the amount of insoluble substances in the lead ion-rich solvent nor does the pretreated lead plaster provide any substantial amount of water or other electrolyte-diluting liquid.
More specifically, an effective concentration of electrolyte may be retained and reused. That is, in view of the fact that the regenerated lead ion-depleted electrolyte formed after the electrochemical treatment of the dried decomposed lead plaster does not accumulate excessive amounts of water or lead dioxide (PbO) 2 ) The recycled electrolyte can be reused on the pretreated (e.g. kiln heating and optional washing) dried decomposed lead paste to continuously recover metallic lead.
Of course, it should be noted that any solids may be removed from the lead ion-enriched electrolyte and/or the recycled electrolyte (e.g., by sedimentation, centrifugation, filtration, etc.). Since these solids are mainly small amounts of residual lead sulfate and/or lead dioxide, these solids can be fed back to the overall process, or to the desulfurization operation and/or thermal pretreatment, as shown in fig. 1. Also, when the electrolyte comprises residual soluble sodium sulfate, it should be appreciated that such sulfate can be readily removed by a variety of means, including precipitation, crystallization, and/or ion exchange.
In particular, the lead ion-rich electrolyte may further comprise residual solid grid lead, and the method may further comprise filtering (after alkane sulfonic acid/MSA) to remove any residual solid grid lead.
Examples
In a first set of experiments, the inventors began to determine heating conditions that allowed for removal of moisture from the lead paste (e.g., unwashed, washed, desulphurised, unhydrogenated or otherwise), which is typically or comprises water or other aqueous solution in the washing step and/or desulphurisation step. The paste was heated at 100 to 105 ℃ and the evaporation of the liquid phase was measured as weight loss. Fig. 2 depicts exemplary results over a temperature range of 20 ℃ to 650 ℃. Notably, significant water removal occurs at temperatures in excess of 220 ℃ (well above the boiling point of water). Advantageously, at such and higher temperatures, the lead plaster not only loses weight due to evaporation, but also undergoes weight lossA significant phase change is observed at increasing temperatures as the heating period extends. For example, fig. 3 shows exemplary results of heating a lead paste at an oven temperature of 525 ℃ in 10 minute increments. As can be easily seen from the pictures, the color change is significant over time, indicating that from PbO x (1<x<2) Transition to PbO (tetragonal). Similarly, when different desulfurized lead paste samples were subjected to different temperatures, respectively, the oxidation state was easily distinguished, starting with the original lead paste (raw lead paste) and ending with PbO (orthorhombic at 670 ℃), as shown in FIG. 4.
Then, the inventors studied whether different temperatures of the lead plaster treatment have an effect on the dissolution/residue of the lead plaster thus treated in an electrolyte, in particular in methanesulfonic acid. More specifically, samples at different temperatures were digested with MSA. Here, 10g of the heat treated material was added to 100ml of 20% msa and allowed to stir for 1 hour. The solids were filtered off and re-weighed and the filtrate was analyzed for dissolved lead ions. Fig. 5 and 6 show exemplary results. As can be readily seen from the data, the heat treatment of the lead plaster at elevated temperatures significantly reduced the amount of undissolved residues (fig. 5), while the amount of lead ions in the MSA significantly increased (fig. 6). Also interesting, two types of PbO crystal structures were found: alpha and beta. Beta configuration and lead oxide (Pb) at 529 DEG C 3 O 4 ) And converted into PbO. At higher temperatures, the tetragonal crystal forms transform to more tightly bound orthorhombic crystal forms. This overall reconfiguration can be observed in the case of shrinkage of the material in the 400 ℃ region and final hardening in a high temperature kiln test exceeding 600 ℃. Thus, a temperature of 600 ℃ is generally less preferred, while a temperature below 450 ℃ will produce a lower amount of electrolyte-soluble lead form. Following a similar procedure as described above, the following results were observed, as shown in table 1 below:
Table 1.
Based on the above batch results in table 1, the inventors have subsequently studied various continuous heat treatment schemes, especially using a rotary kiln, wherein the feed end of the rotary kiln receives desulphurized lead plaster and the discharge end releases the heat treated lead plaster. Exemplary rotary calciners (kilns) have a rotary housing, a belt, an ear-shaft wheel assembly, a thrust roller, a feed/discharge flue with a purge rotary expansion bellows seal, a variable speed chain drive, an integral base frame with adjustable grade, an electric furnace, a water spray cooler, a removable housing flight drum, a removable feed/discharge external baffle (knocker), a removable internal scraper, a removable base thermocouple assembly, a removable feed dam with helical blades, a screw feeder with hopper, emission control equipment, and control instrumentation.
The rotating housing is sized for an outer diameter 7 1/4"O.D.x 6/2" I.D.x 11' -3 "over the entire length and includes a 6' -8" long heating section and a 3' -0 "long cooling section. The housing is made of a centrifugal casting type HH type alloy. Heat is indirectly provided by radiation and conduction as the primary heat transfer means through a 54kW electric furnace with four independent temperature control zones. The electric furnace includes heating elements mounted in the furnace fiber insulation and is designed to allow for precise temperature distribution over the heated length of the kiln. The housing zone temperature for each of the four zones was measured by a type K thermocouple and the current intensity of the zone heating element was controlled by the SCR controller to maintain the housing zone temperature at its design set point. Cooling is performed by indirect water spraying on the outer surface of the housing. The water spray device is contained by a housing surrounding the casing, which is provided with a top spray manifold, a bottom drain connection and a labyrinth end seal. The housing is supported by two belts, each straddling a set of two ear shaft wheels. The bearings of each trunnion axle are mounted on an adjustable spacer that is attached to the unitary base frame. The thrust rollers are located on either side of the feed end belt and are mounted on an adjustable pad that is connected to the integral base. The thrust rollers maintain the housing in its proper longitudinal position. The residence time of the material in the kiln is controlled by the slope and speed of the housing. By pivoting the support base frame to the desired position, the housing grade may be adjusted.
In addition to providing an optional inert purge gas through the housing, the following areas of the apparatus may also be purged with inert gas: the device comprises a feeding and discharging corrugated pipe sealing piece, a feeding and discharging sealing matching surface, a feeding machine, a product collecting barrel and an observation port. Purge gas (air) is most commonly used to minimize solid oxidation and prevent off-gas fires. Purge gas may be metered by a rotameter and delivered through a valve manifold connected to two supplies, one on-line supply and one ready supply (typically 12 cylinder banks) to allow for uninterrupted purge flow. The emission control devices include flame hoods, jiao Youdi, water jacket condensers, venturi water jet scrubbers, packed bed scrubbers, cyclones, baghouses, exhaust fans, and interconnecting ductwork. The scavenge air is discharged to the atmosphere through the kiln and the discharge equipment.
When the raw material is heated, surface moisture first evaporates, and then lead hydroxide and lead dioxide are converted into lead monoxide. When the highest quality product is obtained at the target product temperature of 530 ℃ (+/-7 ℃), the calcined material undergoes a variety of color changes from red to orange to yellow. If the calcined material is overheated, the material color reverts to orange, becoming less brittle.
For an exemplary operation, the rotary kiln was arranged for counter-current operation, the shell speed was set at 5rpm, and the shell grade was set at 0.8 degrees (°) to achieve the predicted residence time. In all experiments, the feed rate remained unchanged. The shell zone temperature is adjusted to achieve the desired color characteristics for the target product temperature of 530 c. In the steady state, the following results are obtained as shown in table 2 below.
Table 2. Process summary-discharge end:
table 3. Summary of process-feed end:
referring to tables 2 and 3, the desired results were obtained when the feed material size was reduced (e.g., less than 1 "maximum size), the shell temperature at the furnace feed end was limited to a maximum of 580 ℃ and operated at 560 ℃ at normal temperatures, and the shell temperature at the furnace feed end was limited to a maximum of 770 ℃ and operated at 730 ℃ at normal temperatures. These conditions are typical conditions for achieving a global yellow product that exits the kiln at a temperature of about 520 ℃ to 530 ℃, primarily the PbO (tetragonal form) content (i.e., pbO 2 The conversion to PbO is at least 60mol%, or at least 70mol%, or at least 80mol%, or at least 85mol%, or at least 90 mol%). Thus, no size of the washed lead paste feed material exceeds 1 inch, regardless of shape.
As used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural referents unless the context clearly dictates otherwise. Also, as used in the description herein, unless the context clearly indicates otherwise, the meaning of "in". Includes "in". And "on",.
Furthermore, as used herein, unless the context indicates otherwise, the term "coupled to" is intended to include both direct coupling (where two elements coupled to each other are in contact with each other) and indirect coupling (where at least one additional element is located between the two elements). Thus, the terms "coupled to" and "coupled with" are used synonymously. Moreover, unless the context dictates otherwise, all ranges set forth herein should be construed to include their endpoints and open-ended ranges should be construed to include only commercially viable values. Likewise, unless the context dictates otherwise, a list of all values should be interpreted to include intermediate values.
However, it will be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. Accordingly, the inventive subject matter is not limited except as by the spirit of this disclosure. Moreover, in interpreting the disclosure, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms "comprises" and "comprising" should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced.

Claims (65)

1. A method of retaining electrolyte in an electrochemical lead recovery operation that recovers metallic lead from a desulphurised lead acid battery lead plaster, the method comprising:
providing a desulphurized lead plaster, wherein the desulphurized lead plaster comprises lead dioxide and at least one of lead hydroxide and lead carbonate, and further comprises residual sulphate;
washing the desulphurized lead paste, thereby forming a washed desulphurized lead paste comprising residual water;
heating the washed desulphurised lead plaster to reduce the residual water to 10wt% or less and reduce at least 25% of the lead dioxide to lead monoxide, thereby forming a dry, decomposed desulphurised lead plaster;
combining the dried decomposed and desulphurised lead plaster with recycled electrolyte to form a lead ion-enriched electrolyte; and
subjecting said lead ion-enriched electrolyte to said electrochemical lead recovery operation, thereby recovering metallic lead at the cathode and producing said recycled electrolyte,
wherein the recycled electrolyte is an acid electrolyte.
2. The method of claim 1, wherein the desulphurized lead plaster is desulphurized using an aqueous base.
3. The method of any one of claims 1 to 2, wherein residual sulfate in the desulphurized lead paste is present in an amount of 0.1wt% to 10 wt%.
4. The method of any one of claims 1 to 2, wherein at least 50% of residual sulfate is removed from the desulphurized lead paste by washing with water.
5. The method of any one of claims 1 to 2, wherein at least 70% of residual sulfate is removed from the desulphurized lead paste by washing with water.
6. The method of any one of claims 1 to 2, wherein at least 90% of residual sulfate is removed from the desulphurized lead paste by washing with water.
7. The method according to any one of claims 1 to 2, further comprising the step of subjecting the desulphurised lead plaster to a pressure filtration step prior to the washing step.
8. The method of any one of claims 1-2, further comprising removing the residual water from the washed desulphurized lead paste.
9. The method of claim 8, wherein removing the residual water comprises pressure filtration and/or using waste heat from the step of heating the washed desulphurised lead plaster.
10. The method of any one of claims 1 to 2, wherein the step of heating the washed desulphurised lead plaster reduces the residual water to equal to or less than 5wt% of the dried decomposed desulphurised lead plaster.
11. The method of any one of claims 1 to 2, wherein the step of heating the washed desulphurised lead plaster reduces the residual water to equal to or less than 2wt% of the dried decomposed desulphurised lead plaster.
12. The method of any one of claims 1 to 2, wherein the step of heating the washed desulphurised lead paste reduces at least 50% of the lead dioxide present in the washed desulphurised lead paste to lead monoxide.
13. The method of any one of claims 1 to 2, wherein the step of heating the washed desulphurised lead paste reduces at least 70% of the lead dioxide present in the washed desulphurised lead paste to lead monoxide.
14. The method of any one of claims 1 to 2, wherein the step of heating the washed desulphurised lead paste reduces at least 90% of the lead dioxide present in the washed desulphurised lead paste to lead monoxide.
15. The method according to any one of claims 1 to 2, wherein the heating step is performed in a kiln such that the temperature of the dried de-desulphurised lead plaster at the end of heating is 400 ℃ to 700 ℃.
16. The method according to any one of claims 1 to 2, wherein the heating step is performed in a kiln such that the temperature of the dried de-desulphurised lead plaster at the end of heating is 500 ℃ to 560 ℃.
17. The method according to any one of claims 1 to 2, wherein the heating step is performed until the temperature of the dried decomposed and desulphurized lead plaster is 500 ℃ to 560 ℃, and wherein the heating step is performed such that the dried decomposed and desulphurized lead plaster is maintained at a temperature of 500 ℃ to 560 ℃ for a time of 0 to 10 minutes.
18. The method of any of claims 1-2, wherein the recycled electrolyte comprises alkane sulfonic acid.
19. The method of any one of claims 1-2, wherein the recycled electrolyte comprises methanesulfonic acid.
20. The method of any one of claims 1 to 2, wherein the electrochemical lead recovery operation uses a moving cathode.
21. The method of any one of claims 1 to 2, wherein the electrochemical lead recovery operation comprises the step of reducing lead ions on one portion of a cathode while removing metallic lead from another portion of the cathode.
22. The method of any one of claims 1 to 2, further comprising the step of removing solids from the lead ion-enriched electrolyte and/or the recycled electrolyte.
23. The method of claim 22, wherein the solid comprises at least one of lead dioxide, lead sulfate, and grid lead.
24. The method of any one of claims 1 to 2, wherein the metallic lead has a purity of at least 95%.
25. The method of any one of claims 1 to 2, wherein the metallic lead has a density of less than 5g/cm 3 。
26. The method of any one of claims 1 to 2, wherein the metallic lead has a density of less than 2g/cm 3 。
27. A method of reducing lead dioxide accumulation in an electrochemical lead recovery operation that recovers metallic lead from a lead plaster of a lead acid battery and uses and recycles an electrolyte in which lead dioxide is insoluble, the method comprising:
providing the lead plaster, wherein the lead plaster comprises lead dioxide and not more than 2.0wt% of sulfate;
heating the lead paste to reduce at least 50% of the lead dioxide to lead monoxide, thereby forming a decomposed lead paste;
combining the decomposed lead paste with a recycled electrolyte to form a lead ion-enriched electrolyte; and
subjecting the lead ion-enriched electrolyte to an electrochemical lead recovery operation to recover metallic lead at the cathode and produce the recycled electrolyte.
28. The method of claim 27, wherein the lead paste is a desulphurized lead paste.
29. The method of any one of claims 27 to 28, wherein the lead plaster comprises residual water in an amount of at least 10wt%.
30. The method according to any one of claims 27 to 28, further comprising the step of subjecting the lead plaster to a pressure filtration step prior to the heating step.
31. The method of any one of claims 27 to 28, wherein the step of heating the lead plaster reduces at least 60% of the lead dioxide to lead monoxide.
32. The method of any one of claims 27 to 28, wherein the step of heating the lead plaster reduces at least 70% of the lead dioxide to lead monoxide.
33. The method of any one of claims 27 to 28, wherein the step of heating the lead plaster reduces at least 90% of the lead dioxide to lead monoxide.
34. The method of any one of claims 27 to 28, wherein the step of heating the lead plaster reduces residual water in the decomposed lead plaster to less than 10wt%.
35. The method of any one of claims 27 to 28, wherein the step of heating the lead plaster reduces residual water in the decomposed lead plaster to equal to or less than 5wt%.
36. The method of any one of claims 27 to 28, wherein the heating step is performed in a kiln such that the temperature of the decomposed lead plaster at the end of heating is 550 ℃ to 570 ℃.
37. The method of any one of claims 27 to 28, wherein the heating step is performed in a kiln such that the temperature of the decomposed lead plaster at the end of heating is 530 ℃ to 550 ℃.
38. The method of any one of claims 27 to 28, wherein the recycled electrolyte comprises alkane sulfonic acid.
39. The method of any one of claims 27 to 28, wherein the recycled electrolyte comprises methanesulfonic acid.
40. The method of any one of claims 27 to 28, wherein the electrochemical lead recovery operation uses a moving cathode.
41. The method of any one of claims 27 to 28, wherein the electrochemical lead recovery operation comprises the step of reducing lead ions on one portion of a cathode while removing metallic lead from another portion of the cathode.
42. The method of any one of claims 27 to 28, further comprising the step of removing solids from the lead ion-enriched electrolyte and/or the recycled electrolyte.
43. The method of claim 42, wherein the solid comprises at least one of lead dioxide, lead sulfate, and grid lead.
44. The method of any one of claims 27 to 28, wherein the metallic lead has a purity of at least 95%.
45. The method of any one of claims 27 to 28, further comprising the step of casting the metallic lead ingot or the metallic lead into a desired shape.
46. The method according to any one of claims 27 to 28, further comprising the step of: collecting water from a heating step or from a step of pressure filtering the lead plaster prior to the heating step, and using at least some of the water in the electrochemical lead recovery operation.
47. The method of any one of claims 27 to 28, wherein the metallic lead has a density of less than 5g/cm 3 。
48. The method of any one of claims 27 to 28, wherein the metallic lead has a density of less than 2g/cm 3 。
49. A method of retaining an effective concentration of electrolyte and reducing accumulation of lead dioxide in the electrolyte in a continuous electrochemical lead recovery operation that recovers metallic lead from a desulphurised lead acid battery lead plaster, the method comprising:
Providing a desulphurized lead plaster, wherein the desulphurized lead plaster comprises lead dioxide and at least one of lead hydroxide and lead carbonate, and further comprises residual sulphate;
washing the desulphurised lead plaster, thereby forming a washed desulphurised lead plaster comprising from 10wt% to 30wt% residual water present in the desulphurised lead plaster;
heating the washed desulphurised lead plaster to reduce the residual water to 10wt% or less and reduce at least 50% of the lead dioxide to lead monoxide, thereby forming a dry, decomposed desulphurised lead plaster;
combining the dried decomposed and desulfurized lead plaster with an electrolyte to form an electrolyte rich in lead ions; and
subjecting the lead ion-enriched electrolyte to the electrochemical lead recovery operation, thereby recovering metallic lead at the cathode and producing a recycled electrolyte,
wherein the recycled electrolyte is an acid electrolyte.
50. The method of claim 49, wherein the desulphurized lead paste is desulphurized using an aqueous base.
51. The method of any one of claims 49 to 50, wherein residual sulfate in the desulphurised lead plaster is present in an amount of 0.1wt% to 10 wt%.
52. The method of any one of claims 49 to 50, wherein washing with water removes at least 60% of residual sulfate from the desulphurised lead plaster.
53. The method of any one of claims 49 to 50, further comprising the step of subjecting the desulphurised lead plaster to a pressure filtration step prior to the washing step.
54. The method of any one of claims 49 to 50, wherein the step of heating the washed desulphurised lead plaster reduces the residual water to equal to or less than 5wt% of the dried decomposed desulphurised lead plaster.
55. The method of any one of claims 49 to 50, wherein the step of heating the washed desulphurised lead paste reduces at least 60% of the lead dioxide present in the washed desulphurised lead paste to lead monoxide.
56. The method of any one of claims 49 to 50, wherein the heating step is performed in a kiln such that the temperature of the dried de-desulphurised lead plaster at the end of heating is 500 ℃ to 560 ℃.
57. The method of any one of claims 49 to 50, wherein the heating step is performed until the temperature of the dried decomposed and desulphurized lead paste is 500 ℃ to 560 ℃, and wherein the heating step is performed such that the dried decomposed and desulphurized lead paste is maintained at a temperature of 500 ℃ to 560 ℃ for a time of 0 to 10 minutes.
58. The method of any one of claims 49 to 50, wherein the heating step is performed in a kiln, wherein the washed desulphurised lead plaster is provided to the kiln, and wherein the washed desulphurised lead plaster has a size of no more than 1 inch in any dimension.
59. The method of any one of claims 49 to 50, wherein the recycled electrolyte comprises alkane sulfonic acid.
60. The method of any one of claims 49 to 50, wherein the recycled electrolyte comprises methanesulfonic acid.
61. The method of any one of claims 49 to 50, wherein the electrochemical lead recovery operation uses a moving cathode.
62. The method of any one of claims 49 to 50, wherein the electrochemical lead recovery operation comprises the step of reducing lead ions on one portion of the cathode while removing metallic lead from another portion of the cathode.
63. The method of any one of claims 49 to 50, further comprising the step of removing solids from the lead ion-enriched electrolyte and/or the recycled electrolyte, wherein the solids comprise at least one of lead dioxide, lead sulfate, and grid lead.
64. The method of any one of claims 49 to 50, wherein the purity of the metallic lead is at least 95%.
65. The method of any one of claims 49 to 50, wherein the metallic lead has a density of less than 5g/cm 3 。
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